DALLAS — The Dallas FBI will help police determine whether a former city employee intentionally lost 22 terabytes of evidence and other files while the city looks for a law firm to conduct an outside forensic audit of the data debacle, officials said on Friday.

Albert Martinez, executive assistant police chief, told a new city committee looking into the matter that Chief Eddie Garcia met on Tuesday with Matthew J. DeSarno, special agent in charge of the FBI’s Dallas bureau.

“We needed outside expertise,” Martinez said.

DeSarno agreed to help the police department’s public integrity unit look into the circumstances of the data deletion events to determine whether a crime was committed, he said.

The police department initially looked into it but couldn’t conclude whether the data deletion was intentional, Martinez said. But since then, the department has learned that the same information technology worker also reportedly lost data on two other occasions, he said.

That additional data loss is what prompted the police chief to reach out to the FBI, which has cybercrime expertise.

Separately, the city’s newly formed Ad Hoc Committee on General Investigating and Ethics voted on Friday to direct the city attorney to reach out to local law firms about handling an outside audit of the incident.

City Attorney Chris Caso said he hopes to be able to provide the committee with a list of the top three firms in about 30 days. The committee would then recommend a law firm to the City Council for approval.

Then the chosen law firm would hire a computer forensic company to help determine what happened and how to prevent future data losses.

The city’s information technology department plans to conclude its own internal review of the incident by Sept. 30, said Chief Information Officer Bill Zielinski. That report is also expected to detail how much of the lost data has been recovered, he said.

The employee, who was fired in late August, has declined to comment to The Dallas Morning News.

During an audit of the city’s records, officials said they discovered a total data loss of about 22.5 terabytes, which is the equivalent of about 7,500 hours of HD video; about 6 million photos; or 150 million pages of Microsoft Word documents.

The first batch of missing data involved cases from one to three years ago, Martinez has said. The time frame for the latest missing evidence is still uncertain, he said.

Regarding the first batch of missing data, the former employee was supposed to move 35 terabytes of archived police files from online storage to a physical city drive starting March 31, city officials have said.

It was supposed to take around five days to move the information. But the employee “failed to follow established procedure” and wound up deleting 22 terabytes from the city’s network drive.

It is unclear what types of crimes or how many cases are involved. The city also said it’s possible the internal audit will uncover more missing evidence.

Garcia has said it’s “more likely than not” violent crimes against people aren’t among the cases affected by the deleted evidence.

Erin Nealy Cox, the former U.S. Attorney in Dallas, spoke to the council after being invited to provide her insight. Nealy Cox, who has a background in cybercrime, resigned as the city’s top federal prosecutor in January after serving in that role since 2017. She said she joined the local law firm, Kirkland & Ellis, as a partner about two weeks ago.

She said the scope of the city’s outside inquiry should be narrowly defined given that parallel investigations are studying different elements of the problem, such as possible criminal involvement. Whichever law firm is selected will interview witnesses, review documents, examine the cloud archive and servers that were involved, among other forensic techniques, she said.

Nealy Cox also said the FBI will likely perform an initial inquiry, or assessment. And if it finds evidence pointing to a crime, the FBI will coordinate with the U.S. attorney’s office on a full-scale criminal investigation, she said.

Brad Lollar, an assistant public defender, told the committee on Friday that he is handling 11 capital murder cases from the Dallas police department, in addition to two other murder cases.

Four of those are set for trial before the end of the year, he said.

“I cannot tell them right now whether we have all the evidence.”